SentryGraphQLHttpFailedRequestHandler improved issue grouping.

[ericsampson]

Fixes #4759

• #4759

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Applies the same improvements for GraphQL as in this PR for plain HTTP: https://github.com/getsentry/sentry-dotnet/pull/4724

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 73.94%. Comparing base (42243df) to head (b74ff29).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4762      +/-   ##
==========================================
+ Coverage   73.85%   73.94%   +0.08%     
==========================================
  Files         485      485              
  Lines       17689    17691       +2     
  Branches     3497     3497              
==========================================
+ Hits        13065    13081      +16     
+ Misses       3762     3750      -12     
+ Partials      862      860       -2     

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